Real-time quantitative PCR based sensitive detection and genotype discrimination of Pepino mosaic virus.

Over the last decade a new virus disease caused by Pepino mosaic virus (PepMV) has been threatening the tomato industry worldwide. Reliable detection is vitally important to aid disease control. Methods must be both sensitive and capable of detecting the range of distinct genotypes that have been identified. The development of five new reverse transcription real-time quantitative PCR (RT-qPCR) assays is described, which allow the detection of all known PepMV genotypes. The performance of the assays was evaluated on Peruvian, European tomato, Ch2 and US1 PepMV genotypes and optimised for both two- and one-step RT-qPCR detection formats. One-step RT-qPCR detected PepMV European tomato genotype particles at least two orders of magnitude more sensitively than ELISA. The method detected as little as one naturally infected seed among 5000 uninfected seeds. The genotype-specificity of the five assays was compared using PepMV isolates representing all of the different genotypes. The following genotype combinations were all discriminated successfully: European tomato-Peruvian, Ch2, and US1. In addition to its application for diagnostic purposes, the genotype-specificity and the quantitative potential of the method, makes it very useful for epidemiological studies or for studies evaluating resistance of plants to virus infection.